Analysis of high multiplicity events

The experimental studies of the high multiplicity events in proton interactions are carried out on U-70 accelerator in Protvino. It is suggested that the collective phenomena can be discovered since the high density matter can be formed in this very region. The collective behavior of secondary particles can manifest in the Bose-Einstein condensation of pions, Vavilov-Cherenkov gluon radiation, excess of soft photon yield and other unique phenomena.     

Wavelets applied to very high multiplicity events

Wavelets are widely used now for the analysis of local scales (or frequencies) important in physical events, biological objects, natural phenomena, etc. They provide unique information about scales at different locations. In particular, they are used for analysis of patterns in the phase space of very high multiplicity events.     

Scaling violation favouring high multiplicity events at 540 GeV CMS energy

New data are presented on the charged multiplicity distribution for non single-diffractive events produced in pp? interactions at a CM energy $\text{s}\text{= 540}\text{GeV}$. The distribution in the full pseudorapidity range is compared with data from the ISR. Using the scaling variable $\text{z =}\text{n}\text{〈n〉}$ a change of shape is observed. The effect is manifested as an increase from 2% to 6% in the proportion of high multiplicity (z > 2) events. For the central pseudorapidity range, |η| ? 1.5, scaling is approximately valid up to $\text{s}\text{= 540}\text{GeV}$.     

On the particle multiplicity distributions at high energy

An experiment has been performed to study the inclusive photoproduction of π⁰ mesons. Photoproduced π⁰'s were detected in a hodoscope consisting of 14 lead glass Cerenkov counters. To obtain the cross sections at a photon energy of 6 GeV we used the photon-difference method. Data are presented in terms of the Feynman variable $\text{x = q}{}_6{}^1\text{(√s/2)}$ and the trnasverse momentum q⊥. We have measured four q⊥ distributions at x = 0.2, 0.4, 0.6 and 0.8. The results dhow that the π⁰ rate at small values of q⊥ is smaller than the π± rate. The data can be fitted smoothly by a form A exp (?Bq_⊥²) with a value about 3.5 GeV^?2 for the slope parameter B.     

Analysis of fluctuation structure in high multiplicity events in ultra relativistic nucleus collision

Two methods for analyzing the fluctuation in high multiplicity events of high energy heavy ion collision are presented. One is for the pseudo-rapidity distribution based on the Multi-Chain-Model (MCM), the other involves Fourier analysis of the azimuthal distribution. Two cosmic ray events are analyzed by the former, and it is found that the fluctuation in both events are smaller than MCM prediction. Through the latter method four events are analyzed, one of them exhibits almost isotropy in azimuth, while smaller probabilities are estimated for the other three events comparing to the isotropic noncorrelated background.     

On hadron multiplicity ine + e − events induced by massive quarks

We analyse the difference in the energy behaviour of hadron multiplicities associated withe ⁺ e ^– events induced by light and heavy quarks in the framework of two approaches: the so-called Naïve Model and the QCD-motivated one. Expectations of both approaches are presented in comparison with the existing data (LEP, SLC).     

Very high energy multiplicity distributions

Within a geometrical model developed in earlier papers, a change of regime, or a “knee,” is predicted in the multiplicity distributions at large multiplicities. The position and motion of this knee is related to geometrical and KNO scaling and their violation, in particular, the rise of the ratio σ_el/σ _t , as well as to the transition from shadowing to antishadowing, expected at LHC energies.     

Proton interactions with high multiplicity

Project Thermalization is aimed to study the proton-proton interaction with high multiplicity of secondary particles. The region of high multiplicity is especially actual at present. We expect the manifestation of the secondary particle collective behavior at this region. The experimentally measured topological cross section was corrected for apparatus acceptance and detection efficiency. These data are in good agreement with gluon dominance model. The comparison with other models is also done and shows no essential deviations. There is evidence that Bose-Einstein condensation can formed at high total multiplicity region.     

On the temperature dependence of quarkonium correlators

I discuss the temperature dependence of quarkonium correlators calculated in lattice QCD. I show that the dominant source of the temperature dependence comes from the zero-mode contribution, while the temperature dependence associated with the melting of bound states is quite small. I study the zero-mode contribution quantitatively for various quark masses and show that it is well described by a quasi-particle model with temperature-dependent heavy quark mass. As a byproduct, an estimate of the medium dependence of the heavy-quark mass is obtained.     

Radiative corrections for baryonic correlators

We reanalyse the first order radiative corrections of the bare loop and of the quark condensate for nucleon and delta two-point function. It turned out, that there were changes in the next to leading order for the logarithms.     

A model for multiplicity distributions in high energy collisions

A phenomenological model is presented which regards the system after collision as a single entity that emits hadrons directly. The evolution of this entity gives a new two parameter distribution which fits the high energypp, \(\bar pp\) ,e ⁺ e ^?, π⁺ p andK ⁺ p data reasonably well. The entity emits hadrons along the rapidity axis and exhibits intermittency behaviour under certain conditions.     

Toward very high multiplicity event generator

The generating functional for probabilities is derived for the scalar model of Yang-Mills fields in terms of functional integrations. The example of 2 → 2 scattering is shown and problems that arise are mentioned.     

Development of a honeycomb gas proportional counter array for photon multiplicity measurements in high multiplicity environment

A novel gas-based detector using large arrays of honeycomb cells has been developed and tested for use as a pre-shower photon multiplicity detector (PMD) for STAR and ALICE experiments. The appropriate cell design was arrived at using GARFIELD simulations. Prototype chambers with cell dimensions corresponding to STAR and ALICE were fabricated and tested at CERN PS and SPS. The charged particle detection efficiency and the pre-shower characteristics have been studied using pion and electron beams.     

Charged particle multiplicity in three-jet events and two-gluon systems

The charged particle multiplicity in hadronic three-jet events from Z decays is investigated. The topology dependence of the event multiplicity is found to be well described by a modified leading logarithmic prediction. A parameter fit of the prediction to the data yields a measurement of the colour factor ratio C_A/C_F with the result